Such a device and such a method are known from WO 03/016944 A2. In the case of the known device and the known method, light pulses are transmitted from a light source to an object surface and reflected there. The light reflected on the object surface goes to an image converter manufactured using CMOS technology, which image converter has a multiplicity of photodetectors in which the incident light stream can generate charge carriers when the photodetector is activated. The photodetectors can be activated for a variable time window. The quantity of charge present in the photodetector at the end of the time window is a measure of the light quantity which has been detected by the photodetector during the time window. By means of the photodetector, the incident light stream is therefore integrated during the time window.
By varying the time interval between the process of emission of the light pulse and the time window used for integration, a correlation function between the light pulse and the time window can be determined. If the duration of the light pulses is equal to the duration of the time window, the correlation function has a pronounced maximum. The maximum of the correlation function lies at a time value which corresponds to the light propagation time of the light pulse from the light source to the photodetector. The light propagation time can therefore be determined directly from the maximum of the correlation function. The distance between object surface and device can then be calculated from the light propagation time.
The known device and the known method can be used in the fields of automotive engineering, navigation or building engineering, safety engineering and automation.
One disadvantage of the known device and of the known method is that objects lying partially concealed, for example on a vehicle behind a fence or a bush, are not recognized correctly. Likewise, dust or other contamination on the optical system can lead to incorrect measurements. In the known method and the known device, an average distance value is displayed for objects lying partially concealed, said average distance value being produced from the averaging of various distance values.